Judiciary Committee Chairman Rep. John Conyers (D-Mich.) and several of his colleagues have asked the Government Accountability Office to investigate allegations that Arbitron's Portable People Meters undercount minorities.

That came in a letter to GAO, according to Conyer's office, and opens up a third front in the government's query into the ratings technology.

The House Oversight and Government Reform Committee is also looking into the allegations, and the FCC has an ongoing inquiry as well.

Although Portable People Meters are primarily a radio issue, the FCC does use Arbitron markets in its multiple ownership rules, which determine in what markets TV, radio and newspapers can be co-owned.

The Oversight Committee investigation was partly prompted by complaints from some of the Brooklyn constituents of committee Chairman Edolphus Towns (D-N.Y.).

Arbitron had no comment on the Conyers initiative, but said of the Townes investigation when it was launched that the company was happy to talk about the meters with Congress, the FCC and stakeholders, pointing out it has already been doing that, as well as making improvements to the technology as a result of that dialog.